正则表达式只允许两个字，一个空格，最多50个字符

Question

I'm trying to build a regular expression with the following conditions:

• Only two words
• allow one space after the last word
• Maximum length 50

like ("firstname lastname ")

Thanks.

Answer 1

Try this:

 const validate = data => /^\\w+\\s*\\w+ ?$/.test(data) && data.length <= 50 const testData = ['this works', 'this too ', ' this fails', 'firstname lastname ', ' firstname middlename lastname '] for (let temp of testData) { console.log(`${temp} ${validate(temp)}`) } 

Answer 2

Here is a regex which covers all your requirements, including the length check:

^(?!.{51,})(\w+\s+\w+ ?)$

Explanation:

^(?!.{51,})    assert that the string is not followed by 51 or more characters
(
    \w+        match a word
    \s+        followed by one or more spaces
    \w+        followed by a second word
     ?         ending with an optional space
)$

 function tests(str){ var regex = /^(?!.{51,})(\\w+\\s+\\w+ ?)$/; if (regex.test(str)) { console.log("passes"); } else { console.log("fails"); } } tests("firstname lastname "); // passes tests("first name last name"); // fails tests("123456789 1234567890123456789012345678901234567890"); // passes (length 50) tests("123456789 12345678901234567890123456789012345678901"); // fails (length 51) 

Regex 101

Answer 3

 function tests(str){ var pat=/^[a-zA-Z]+\\s[a-zA-Z]+\\s?$/; if(pat.test(str) && str.length<=50){ console.log("true"); } else{ console.log("false"); } } tests("firstname lastname "); //true tests("first name last name"); //flase 

Answer 4

You can check word count by splitting string into array like this

var array = "some string".split(" "); //result - ["some","string"]

Now you can check word count

var count = array.length; //will return 2

You can count letters like this

var letterCount = "some string".length; //will return 11

Way easier and better than using regex.

Answer 5

此模式将帮助/^[aZ]+\\s[aZ]+\\s?$/

<input type="text" pattern="^[a-Z]+\s[a-Z]+\s?$" title="Must be two words...">